Resilient arthroplasty device

ABSTRACT

The disclosure is directed to a resilient implant for implantation into human or animal joints to act as a cushion allowing for renewed joint motion. The implant endures variable joint forces and cyclic loads while reducing pain and improving function after injury or disease to repair, reconstruct, and regenerate joint integrity. The implant is deployed in a prepared debrided joint space, secured to at least one of the joint bones and expanded in the space, molding to surrounding structures with sufficient stability to avoid extrusion or dislocation. The implant has opposing walls that move in varied directions, and an inner space filled with suitable filler to accommodate motions which mimic or approximate normal joint motion. The implant pads the damaged joint surfaces, restores cushioning immediately and may be employed to restore cartilage to normal by delivering regenerative cells.

RELATED APPLICATIONS

This application is related to provisional application Ser. No.61/135,820, filed on Jul. 24, 2008, which is incorporated herein in itsentirety and which is relied upon for priority.

BACKGROUND OF THE INVENTION

This invention relates to arthroplasty, and more particularly, to animplant for use in arthroplasty. When hyaline articular cartilage isdamaged, it breaks down and joint space is lost. Inflammatory enzymessuch as from the Cox-1, Cox-2 and/or 5-Lox systems, are released andloose bodies form adding to the degradation of joint function. Suchjoint damage is conventionally treated by physical therapy, analgesics,pain medication and injections. When these treatments fail, thetraditionally accepted treatment option is arthroplasty implantation orreplacing the joint with an artificial joint construct. Currentarthroplasty techniques typically use “plastic and metal” implants thatare rigid and which ultimately fail due to loosening or infection.Conventional materials for the artificial joint components includechrome-cobalt-molybdenum alloy (metal) and high molecular weightpolyethylene (plastic). Each is often fixed by a cement-like mixture ofmethyl methacrylate to the ends of the bones that define the joint thatis the subject of the arthroplasty, or coated with a surface thatenables bone ingrowth. Current hip joint replacements typically lastabout 10-15 years and knee replacements typically last about 5-10 years.Ankle joint replacements, on the other hand, are not very successful,and often fail in the first several years after surgery.

Conditions requiring arthroplasty include traumatic arthritis,osteoarthritis, rheumatoid arthritis, osteonecrosis, and failed surgicalprocedures.

SUMMARY OF THE INVENTION

The present invention is directed to an orthopedic implant configuredfor deployment between opposing members of a joint structure thataddresses many of the shortcomings of prior artificial joints. Thearthroplasty implants embodying features of the invention are configuredto preserve joint motions while removing the pain and dysfunctionfollowing the development of arthritis or joint injury. The arthroplastyimplant in accordance with the present invention achieves improvedphysiologic motion and shock absorption during gait and acts as aresilient spacer between moving bones during limb movement. The combinedcharacteristics of the implant include anatomic design symmetry,balanced rigidity with variable attachment connections to at least oneof adjacent normal structures, and durability which addresses and meetsthe needs for repair or reconstruction thus far missed in the prior art.The implant should be secured to at least one of the bones of the jointstructure.

More specifically, the resilient implant embodying features of theinvention has a first wall configured to be secured to a first bone ofthe joint structure by one or more appendages such as a skirt or one ormore tabs and a second wall configured to engage a second and usuallyopposing bone of the joint structure. A side wall extends between thefirst and second walls of the implant and together with the first andsecond walls preferably defines at least in part an inner chamber orspace between the first and second walls. The implant is configured toprovide linear or curvilinear and/or rotational motion between the firstand second bones which mimics or approximates the natural motion betweenthese bones. The inner chamber or space is configured to maintain afiller material therein such as an inflation fluid or a resilientmaterial and preferably to maintain spacing and provide support betweenthe interior of the first and second walls to avoid significant contacttherebetween. The walls of the implant are preferably sealed about theperiphery thereof to maintain the interior chamber in a sealed conditionto avoid loss of inflation fluid or filling media. The side wall orwalls may be formed from the edges or periphery of the first and secondwalls. The properties of the implant walls and the interior arecontrolled to provide the particular resiliency desired for the joint inwhich the implant is to be placed as well as any desired motion betweenthe first and second walls. A conduit may extend from a source ofinflation fluid or other filling medium to the interior of the implantto facilitate expansion of the implant after deployment within thejoint. The inflation fluid may be a gas, a liquid, a gel or a slurry, ora fluid that becomes a suitable resilient solid such as a curablepolymer. Selection of the inflation or interior filling medium maydepend upon the nature of the joint structure in which the implant is tobe deployed, its anatomy, pathophysiology, and the properties of theimplant material.

There may be several alternative embodiments depending upon the site inwhich the implant is to be deployed. For example, the polymer formingthe side wall may be semi-compliant or elastic and the inflation fluidmay be incompressible (e.g., a liquid). Alternatively, the polymerforming the side wall may be non-compliant (non-elastic) and theinflation fluid or filling medium may be compressible, e.g., a gas or aresilient polymeric foam or sponge-like solid that may have a closedcell structure. The first and second walls of the implant need not havethe same properties as the side wall. For example, parts of the implantsuch as the side wall portion may be compliant and the first and secondwall portions in contact with the bone or other joint structure may benon-compliant. Additionally, the various walls or portions thereof mayalso be reinforced with non-compliant or semi-compliant polymer strands,beads or gel coating such as biologic or polymer latticework. Thethicknesses of the first, second and side walls may be varied toaccommodate for the needs of the joint structure from the standpoint ofstrength, elasticity and wear resistance. Moreover, the walls of theimplant may be provided with joint tissue regeneration agents thatrebuild the joint structure in which the implant is deployed. Theregeneration agent may be incorporated into the wall of the implantprior to delivery or placed between the surface of the implant and thejoint structure which it contacts after delivery. All or part of thewalls of the implant may also be made of a biodegradable polymer, byminimally manipulated autograph, allograph or xenograph tissues, or acombination thereof. The method of surgery may incorporate a progressiveapplication of the implant embodiments depending upon clinical needs.

The implant is preferably formed of suitable biocompatible polymericmaterials, such as Chronoflex, which is a family of thermoplasticpolyurethanes based on a polycarbonate structure (Al, the aliphaticversion, Ar, the aromatic version and C, the casting version) availablefrom AdvanSource Biomaterials, Corp. Other polymers include Bionate 80,90A, 55 or 56, which are also thermoplastic polyurethane polycarbonatecopolymers, available from PTG Medical LLC., an affiliate of the PolymerTechnology Group located in Berkeley, Calif. Other commerciallyavailable polymers include Purisil 20 80A which is a thermoplasticsilicone polyether urethane, Carbosil 20 90A which is a thermoplasticsilicone polycarbonate urethane and Biospan which is a segmentedpolyurethane. These polymers are available as tubing, molded or dippedcomponents, solution, pellets, as a casting and as a cast film for theside and first and second walls. The implant may be formed by casting,blow molding or by joining sheets of polymeric material by adhesives,laser welding and the like. Other methods of forming the implant mayalso be suitable. The walls may also be provided with reinforcingstrands which are located on the surface of the walls or incorporatedwithin the walls. The implant material should be biocompatible,non-toxic, and non-carcinogenic and should be resistant toparticulation.

The present invention provides an improved joint implant which isdesigned to endure variable joint forces and cyclic loads enablingreduced pain and improved function. Depending upon the particular jointinvolved there may be linear or curvilinear motion between the first andsecond walls, rotational motion between the first and second walls orboth linear and curvilinear motion and rotation motion between the firstand second walls. Preferably, a space is maintained between the innersurfaces of the first and second walls to avoid erosion and weartherebetween.

The resilient arthroplasty implant embodying features of the inventionis preferably deployed as a minimally invasive procedure to deliver theimplant into a prepared space in a preselected joint structure, whereupon it is inflated to create a cushion, to cover damaged or arthriticcartilage and to be employed to deliver stem cells or livingchondrocytes or other tissue regeneration agents. The goal of suchdeployment is to reduce pain and improve function, to reverse arthritis,to fill in osteochondral defects succinctly, thereby avoiding livingwith both dysfunctional and ablative metal/plastic prostheses or thepathophysiologic state necessitating the procedure. The operative planis simple, systematic, and productive of new joint space with regrowthpotential involving joint debridement by routine arthroscopic methods orsteam application, followed by implantation of the implant. The implantprovides three things, namely a covering or patch for the damaged orworn joint surface, an inflated cushion to pad gait as in normal walkingin the lower extremity, and delivery of regenerative cells on thecartilage remnant surface. The stem cells may be injected as the implantis being expanded and/or directed into the adjacent hyaline cartilagevia an implant coating or perfused cell template. Viscolubricants suchas Synvisc or Hyalgan, analgesics such as Lidoderm, anti-inflammatoryand/or antibiotic coatings as well as those stimulating cell growth mayaccompany the composite external implant. The implant is left in placeas long as feasible, at least until regenerative cells can attach to theadjacent natural joint surface (usually in about 24 hours), or untilwound healing (which may take up to 28 days or more depending on thejoint structure). Preferably, the implant is designed stay within thejoint structure for years, providing inert padding, cushioning and a newcell source. The implant may be used in weight bearing and non-weightbearing interfaces. Animal usage of the implant, such as in horses anddogs, will benefit following hip and knee injuries. The implant isintended primarily for mammalian use.

These and other advantages of the invention will become more apparentfrom the following detailed description and the attached exemplarydrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an idealized jointstructure having first and second bones with an implant having featuresof the invention disposed within the space between the opposing bones ofthe joint structures.

FIG. 2 is similar to FIG. 1 illustrating curvilinear movement betweenthe two opposing bones.

FIG. 3 is a transverse cross sectional view taken along the lines 3-3 inFIG. 1 illustrating rotational movement between the two opposing bones.

FIG. 4 is a perspective view, partially in section, of an implantembodying features of the invention with an enlarged upper portion priorto implantation.

FIG. 5 is an elevational view of the implant shown in FIG. 4 mounted onthe head of a patient's femur.

FIG. 6 is a cross-sectional view of the implant shown in FIGS. 4 and 5deployed between the head of a patient's femur and acetabulum afterrelease of traction to allow for the bones to settle into their naturalalbeit pathologic angles of repose.

FIG. 7 is an elevational view of a resilient arthroplasty implant with asmaller upper portion than that shown in FIGS. 4-6 that has beendeployed between the head of patient's femur and the acetabulum of thepubic bone.

FIG. 8 is an elevational anterior view of a left proximal femur with animplant placed over the femoral head portion of the hip joint as shownin FIG. 7, in partial cross section, to illustrate details thereof.

FIG. 9 is a lateral elevational view of a femur with the implant shownin FIG. 6, as viewed from the “side of the body” or lateral hip aspect.

FIG. 10 is a superior view of a femur with the implant shown in FIG. 7.

FIG. 11 is an inferior view of the hip joint invention iteration orimplant in FIG. 10.

FIG. 12 is a superior or cephalad view of a patient's hip with aresilient implant having features of the invention, viewed from the headof the patient or from a cephalad to caudad direction.

FIG. 13 is a lateral view of the patient's ankle having a resilientarthroplasty device implant which embodies features of the inventionbetween opposing joint structures.

FIG. 14 is a mortise (30 degree oblique AP) view of the patient's leftankle with implant shown in FIG. 13.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention is directed to arthroplasty implants andprocedures for a wide variety of joints such as, for example, hips,knees, shoulders, ankles, elbows, wrists, fingers, toes,temporomandibular joints and the like, but for clarity, as well asbrevity, the discussion herein will focus on an implant for a hip jointand an implant for replacing the talus bone of a patient's ankle.

FIG. 1 is a highly schematic idealized view of an implant 10 embodyingfeatures of the invention that is deployed within a joint structurehaving a first bone 11 and a second bone 12. The implant 10 has a firstwall 13, a second wall 14, and a side wall 15 which define the implantinterior 16 which contains filling material 17. The first wall 13 issecured to the end of the first bone 11 by the skirt 18 that extendsfrom the first wall 13 and the second wall 14 engages the end surface ofthe second bone 12 and may also be secured thereto. The side wall 15extending between the first and second walls 13 and 14 defines at leastin part the implant interior 16 which is filled with filling material17. The inner surfaces of wall 13 and skirt 18 preferably conform to theparticular surface of the head of the patient's first bone 11. The outersurface of the second wall 14 is preferably configured to conform to theend surface of the second bone 12. The drawings are highly schematic anddo not depict details of the joint surface features such as of the endof the first bone 11 or the end of the second bone 12, since humanpathology and variation reflects both the patient's immediate andevolving pathophysiology.

The edge of the implant 10 shown in FIG. 1 has a depending skirt 18 tosecure or anchor the implant to the end of bone 11, but may have one ormore depending tabs that may be employed for similar functions as willbe discussed in other embodiments. The skirt 18 (and/or tabs) maytightly fit about the end of the first bone 11 as shown, or the skirtcan be secured by adhesive (e.g. methyl methacrylate, bone ingrowth) tothe supporting bone structure or be mechanically connected by staples,screws and the like. Moreover, the lower portion of the skirt 18 may besecured by a purse string suture or a suitable strand (elastic or tied)that is tightly bound about the outside of the skirt.

As shown in FIG. 1, the implant interior 16 between the wall 13 and thewall 14 is filled with filler material which aids in maintaining thedesired implant dynamics within the joint structure. The nature of thefiller material such as a fluid and the characteristics of the walls 13,14 and 15 may be selected to maintain a desired spacing between thewalls in order to accommodate the pressure applied by the bones of thejoint structure to the implant 10 and to allow suitable motion betweenthe first and second walls 13 and 14 of the implant 10 which facilitatebone motion which mimics or approximates normal movement for the jointmembers involved such as shown in FIGS. 2 and 3. Alternatively, asmentioned above, the inner chamber may be filled with resilient materialto provide the desired spacing, pressure accommodation, while allowingdesired physiologic motion between implant layers. The implant 10 ispreferably configured to be shaped like the joint space and bonesurfaces being replaced or to fill the void produced by injury ordisease so that the natural joint spacing and cushioning of the jointinterface is restored toward normal physiologic appearance and function.Fluids such as saline, mineral oil and the like may be employed toinflate the implant.

Linear or curvilinear movement between the first and second walls 13 and14 as a result of movement of the first and second bones 11 and 12 isillustrated by the arrow shown in FIG. 2. Rotational movement about thebone axis between the first and second walls 13 and 14 as a result ofaxial rotation between the first and second bones 11 and 12 isillustrated by the arrow shown in FIG. 3. While not shown in thedrawings, there may be slippage between the second bone and the secondwall in addition to wall movements within the implant per se to providedesired joint movements. The skirt 18 is designed to secure the generalimplant to the joint structure so as to avoid dislocation of theimplant. Movement of the joint with the implant 10 in place will be ashared function of both the moving opposing walls 13 and 14 of theimplant but also a function of the movement of the wall 14 which may beless attached to the joint members. There may be slight movement betweenthe skirt 18, wall 13 and the first bone 11. As shown in FIG. 2 one sideof the side wall 15 is in compression and the other is stretched toaccommodate bone interface movement. The walls 13 and 14 may be thickeris some areas to accommodate particular loads and the side wall 15 maybe thinner and more elastic to accommodate rolling and stretchingthereof.

The interior 16 of implant 10 is adjustably filled by the physician froman appropriate source thereof after the implant is deployed to ensurethat the pathologic joint space becomes a resilient cushion again whichaids restoration of worn or damaged cartilage interfaces in the joint bycovering cartilage defects with the implant material, cushioning thejoint and defects therein and delivering cell regeneration agents. Inone embodiment, the arthroplasty implant comprises a bio-compatibleinflatable member that is filled with a biocompatible fill material suchas a gas, liquid, gel or slurry, or fluid that becomes a resilient solidto provide relative movement between the first and second walls 13 and14. The filling or inflation media may be inserted through an injectionvalve site leading to the cannula which delivers the material into theinterior of the implant. In an alternative embodiment, the implant maybe filled with or have an interior formed of biologically compatibleresilient material, e.g. a closed cell sponge filled with suitable fluidthat is inserted into the interior of the implant prior to the implant'sdeployment or injected into the interior after the implant is deployedat the joint site. The interior of the implant may be provided withlubricious material to facilitate movement between the inner wallsurfaces and to minimize contact wear therebetween. The polymeric wallsof the implant may be impregnated with or otherwise carry tissueregeneration agents such as stem cells, living chondrocytes, and/orgenes to repair joint surfaces.

The implant can be used in a variety of joints where the implantreplaces a bone on bone surface and cushions the interaction between thearticular ends of any two bones, such as at the femoral-acetabularinterspace of a patient's hip, the humerus and glenoid scapularcomponent in the shoulder, the femoral tibial and patella femoral kneeinterfaces, the replacement of talus bone in the human ankle between thetibia and calcaneus and the like. Where the implant is substituting orenhancing articular cartilage, the rigidity can be reduced or enhancedto maximize conformation changes that arise during motion as enabled bythe two opposing walls and intended inner space, coupled withconsiderations in any joint surgical reconstruction with accommodationto or amplification of the existing joint ligaments, tendons or dearththereof. The implant 10 may be deflated and removed by minimallyinvasive surgery, for example after the implant has served its purposeof regenerating tissue or if another clinical condition warrants itsremoval. However, it may not be clinically necessary to remove theimplant even if inflation is lost, since the two remaining functions ofpatching the injured cartilage, and delivering restorative cells mayjustify implant retention.

FIG. 4 is a perspective view, partially in section, illustrating a hipimplant 20, similar to that shown in FIG. 1, but with a much largerupper portion. The large upper portion of the implant 20 has a firstwall 21, a second wall 22 and a side wall 23 which define at least inpart the interior 24. Skirt 25 depends from the first wall 21 andsecures the first wall 21 to the end of the patient's femur 26 as bestshown in FIGS. 5 and 6. FIG. 6 illustrates the implant mounted on thehead of the femur 26 with the second wall 22 of the filled upper portionconfigured to engage the corresponding acetabulum 27 of the patient'spelvic bone 28. The skirt 25 surrounds the head of the patient's femur26 and secures the implant 20 thereto. In this embodiment, the enlargedupper portion of the implant creates overlapping layers. The overlappinglayers are directed in opposite directions relative to the interiorportion of the implant such that an overlapping layer is directedtowards the interior portion and an overlapping layer is directed awayfrom the interior portion of the implant, like a redundant membrane, inthe side wall 23 between the first and second walls 21 and 22 toaccommodate the normal movement of the first or second. This providesgreater motion between the femur and the acetabulum and also providesimplant stabilization over the head of the femur 26. This structure alsoaccommodates variation in individual joints that occur from patient topatient.

In the embodiment shown in FIGS. 4-6 the first wall 21 does not extendacross the entire end of the patient's femur as in the embodiment shownin FIGS. 1-3. However, the implant 20 may be designed so that first wall21 may extend over the head of the femur as shown in FIGS. 1-3 (andFIGS. 7-12 discussed hereinafter). The second wall 22 and the side wall23 tend to roll as the femur 26 moves within the acetabulum 27.

Prior to deploying the implant embodying features of the invention, thecartilage lining the joint is prepared by removing hyaline or fibrocartilage flaps or tears, and areas of chondral advanced fissuring areexcised or debrided to create precisely defined defects surrounded bystable normal remnant hyaline cartilage with vertical edges in relationto the damaged surface. It is these defects of the cartilage previouslynormal surface into which new living cells may be injected or otherwiseinserted, and allowed to aggregate by the implant interpositionalarthroplasty proximate expanded compressive external wall material.Synovitis invading the joint periphery may be vaporized and extractedconventionally or by the use of steam. Areas of greater cartilage damageare removed for subsequent regeneration and the less afflicted areashaving stable cracks are treated to seal or weld the cracks. Areas wherethe tugor or consistency or minimally damaged cartilage can be preservedare intentionally saved rather than destroyed so as to support thenormal spacing and gliding opportunity of the more normal jointinterface. Thus, normal cartilage is left behind and abnormal cartilageis removed with the implant making up for the deficiencies. With thepresent invention, it is preferred to avoid joint dislocation so as topreserve natural innervations and vascularity and thus preserving theblood supply afforded by the medial and lateral circumflex arteries forthe hip joint to the femoral head.

Joint preparation is usually performed under a brief general anestheticof outpatient surgery. A muscle relaxant combined with traction (e.g. 60pounds force for a hip implant) opens the joint wider to permit improvedvisualization for joint preparation and implant installation, increasingthe space between the remnant cartilage from about 3 up to about 12 mm.Increasing the space allows the surgeon to wash out noxious enzymes, toremove invasive synovitis, to remove loose bodies, to prepareosteochondral defects ideally and otherwise prepare the joint for theimplant. Partial or complete inflation of the implant will usuallyprecede release of traction. Regeneration agents or cells are insertedwith the implant or as a fluid or 3-D template prior to release oftraction and wound closure. It is preferred to perform jointdebridement, implant deployment and application of cell regenerationagent, e.g. stem cell application, under the same anesthetic. Asdescribed by several companies in the Stem Cell Summit held in New York,N.Y. on Feb. 17, 2009, it is desirable to obtain an aspiration of thepatient's bone marrow from the iliac crest after anesthesial sterilelyat the beginning of the operation. The intraoperative technologist will“dial in the cells” to regenerate areas of maximum pathophysiology whilethe surgeon debrides or otherwise prepares the joint and inserts theimplant, placing the cells at the best time. Cell implantation may alsooccur as a secondary or tertiary reconstructive treatment adjunct.

FIG. 7 is an elevational view, partially in section, of an alternativeresilient implant 30 deployed within a patient's hip structurecomprising the head of the patient's femur 31 and the acetabulum 32 ofthe patient's pelvic hip bone 33. The upper portion of the implant 30 issmaller than that shown in FIGS. 4-6. Details of the interior of thejoint are not provided such as cartilage, ligaments and the like for thepurpose of clarity. The resilient implant 30 embodying features of theinvention is disposed within the space between the femur 31 and theacetabulum 32. FIGS. 7-11 illustrates the implant 30 mounted on the headof femur 31 without the pressure from the acetabulum 32 for purposes ofclarity.

The implant 30 shown in FIGS. 7-12 is shaped like a half an orange rindor a hemisphere for a hip joint. The implant 30 has a first wall 34 seenin FIG. 8 which is secured to the head of the femur 31 by a plurality ofdepending tabs 35. The tabs 35 may be attached to the femur 31 by asuitable adhesive or mechanically such as by a screw or pin. The secondwall 36 of the implant engages the acetabulum 32, but it also may beprovided with tabs and the like for securing the second wall theacetabulum 32.

The side wall 37 extends between the first and second walls 34 and 36 toform an interior 38 which receives filling material 39 through tube 40.The implant 30 would also be appropriate for the humeral head in theshoulder or one condyle of the knee or of the humerus, but other shapesmay be desired for other joint configurations whether relatively flat asin the thumb base, or more inflated toward a ballooning construct as inthe ankle when the talus bone is collapsed. In many embodiments theimplant 30 is a weight bearing spacer that will allow joint motions toapproach normal, whether filling the space left by an entirely collapsedperipheral joint bone or the space of ablated cartilage proximatesurfaces diffusely as in osteoarthritis or succinctly as inosteonecrotic defects or localized trauma. The walls 34 and 36 may beused as a membrane for holding living cells in proximity of theosteochondral defect long enough for the cells to attach (e.g. 24 hours)or to deeply adhere (up to 28 days) or return to normal (up to oneyear). Weight bearing will be expected to increase as distal lowerextremity joints are treated.

Motion is believed to be primarily between the spaced walls of theimplant peripherally secured to joint structures, although some motionmay occur between the implant and the joint surfaces (as with currentbipolar hip hemiarthroplasties). As shown in FIG. 12, the implant 30 maybe provided with a slot 41 extending from the periphery 42 of theimplant to a centrally located passage 43 through the implant toaccommodate the ligament of the head of the femur for hip implants. Kneeimplants (not shown) may have two slots leading to separate passages forreceiving the anterior and posterior cruciate ligaments. Implants forother locations may have similar variable structures to accommodateanatomical features. Implant walls 34 and 36 should have sufficientinherent flexibility to mold to the existing deformities imposed byeither natural ligament, bone, tendon and remaining cartilagedeformities of the internal joint space filled as a cushion. The wallexteriors may be flat or formed with random or specific patterns forpurposes of glide or trends for traction against adjacent surfaces, oras sulci or venues for cell delivery materials.

A separate portal or tube (not shown) or the existing conduit 40, may beused to extract noxious inflammatory enzymes that can be aspirated atappropriate clinical intervals. Inflammatory enzymes in the COX1, COX2and or 5LOX pathways can be extracted. Viscolubricants can be injectedinto the interior of the resilient arthroplasty device through existingconduit 40 or through a long needle to aide in distension, expansion,lubrication (with predetermined microporosity).

The ankle version of the arthroplasty implant 50 of the presentinvention shown in FIGS. 13 and 14 has basically a square transversecross-section that must take into account supratalar ankle dorsi/plantarflexion, subtalar eversion/inversion motions, ligament fixation-needs,and the accommodation to existing bony architecture as implant variablesaccounting for the ipsilateral joint pathophysiology. The implant 50 hasa first wall 51, a second wall 52 and a side wall 53 which extendsbetween the first and second wall. The exterior of the implant 50 mayhave a mesh material 54 with a plurality of chords 55-61 for securingthe implant 50 to adjacent bones or to remnant ligaments which areattached to adjacent bones.

The implant 50 may be inflated with gas and/or liquid to open wider thespace between the tibia above and the calcaneus below to accommodatecollapse of the talus bone as in the flattening which succeeds talusfracture with avascular necrosis, or it may be filled with a liquid thatbecomes a resilient solid. The instant center of the implant's rotationwill be constantly changing, with the talus implant mainly stable andwith the tibia moving over it. Deformation with weight bearing duringthe average human's. 10,000 daily steps or 2-4 million annual gaitcycles required by the stance and walking of normal activities of dailyliving, must be balanced between sufficient solidarity of the implant tomaintain axial load, avoiding circumferential stress, and shear forcesimposed by the tibia distal plafond on the dorsal ankle implant allowingstance and gait of the patient while avoiding implant migration orfailure. Further accommodation to lateral forces imposed by the boneymedial and lateral malleoli, need to be endured through the cyclic loadof walking, while collapsing with enough give to absorb shock and tomatch the shape of surrounding structures of bone and ligament tissue.Whereas the axial load between the distal tibia through the talarimplant to the dorsal calcaneus will be loaded during stance andespecially while walking on a level plane for supratalar motion, thelateral forces will be loaded particularly with subtalar motion whilewalking on an uneven plane or with inversion/eversion.

The dimensions of the various implant walls will vary depending upon thematerial properties thereof as well as the needs for a particular joint.Additionally, the first and second walls may require a thicknessdifferent from the side wall. Generally, the implant may have a wallthicknesses of about 0.125 mm to about 3 mm, preferably about 0.5 mm toabout 1.5 mm. The spacing between the first and second wall within theinterior can vary from about 0.5 mm to about 5 mm for most joints(except for the implant for an ankle when an entire collapsed bone spaceis being replaced), preferably about one to five centimeters to fillbetween the tibia and calcaneus. In the ankle invention version of theimplant, the amount of inflation of the implant per se will be directlyproportional to the amount of talus bone collapse between the distaltibia and proximal calcaneus—thus as much as 5 cm implant distension orexpansion may be required to be maintained between superior and inferiorsurfaces in FIG. 13 of the talus, while as much as 10 cm anterior andposterior expansion may be required for the ankle implant between theposterior soft tissues such including the Achilles tendon and theanterior navicular bone as relates to the talus as seen in FIG. 13.

The method of insertion for the hip joint invention will be a minimallyinvasive approach, ideally arthroscopically facilitated, as long as thesurgical timing and result quality permit smaller incisions. The hippatient will be placed in the lateral decubitus position (lyingnon-operative side down on the operating table) with a stabilizingoperating table pole and pad apparatus positioned to fix the pelvis. Theexternal stabilizing table and attachments will include a padded metalpole beneath the pubis or pelvic bone from posterior to anterior, alongwith other external anterior and posterior pelvic stabilizing paddles.The affected leg will be attached beneath the knee with a distractingmechanism that applies about 60 pounds of distal force to open the hipjoint about 1 cm once the patient is under general anesthesia. The hipjoint is arthroscopically debrided through at least one anterior 0.5 cmincision and one posterior 0.5 cm incision, to remove from the femoralhead acetabular (ball and socket) joint arthritic debris such assynovitis, loose bodies and noxious inflammatory enzymes. In certaincases a larger open incision may be needed. A smoothing orelectronic/ultrasonic/steam or other chondroplasty method may beperformed to make the remaining cartilage smoother to better accommodatethe hip implant, and protuberant osteophytes or lateral bone overgrowthsmay be arthroscopically removed or if needed by open excision. A lateralhip incision may be required between 2 and 10 centimeters in length todeal with deformities and/or to insert the implant. In cases of majordeformities appropriate reconstruction will add to the basic procedure.

Once the joint is open and cleared, the hip implant will be insertedlaterally and fixed via the skirt or tabs to the adjacent structuresincluding the peripheral femoral head and/or acetabular rim. Preferably,the implant is inserted arthroscopically through a cannula about 10 mmin diameter with the implant in the deflated construct, and once insidethe prepared joint space and secured therein by the skirt or tabs, theimplant will be distended or inflated with gas, gel, fluid or fluid thatbecomes a resilient solid to fill the original natural space of about0.5 cm between the upper acetabulum and lower femoral head, covering asmuch of the upper hip joint as required as the implant expands to fitthe space. Tensioning will be by the surgeon's sense of proper pressureapplication aided by a gauged syringe for insertion of viscolubricantssuch as Synvisc, Hyalgan, Supartz and/or analgesics such as lidocainegel. The insertion of liquids to the joint per se may be directly,through a cannula to the joint space previously in place fordebridement, and or via a cannula or tube that is not part of theoriginal implant assembly. Once the joint is cleaned, the implant isinserted and appropriately fixed to avoid extrusion or dislocationthereof. This may be via attachment of the implant tabs and/or by acombination of tab use plus intended friction created by implant surfacecoverings (analogous to Velcro) or a draw string at the smaller base ofthe implant.

The walls of the implant embodying features of the invention may becomposite structures. For example, the innermost layer may be imperviousto preclude escape of inflation or other filling media, a central layermay be porous or otherwise contain treatment or cell regenerationagents, and the outer layer may be a thin, but strong layer of athermoplastic such as a thermoplastic polyurethane which hasmicroporosity sufficient to allow passage or egress of treatment or cellregeneration agents from the central layer. The degree of microporosityto enable egress of treatment or cell regeneration agents from thecentral layer is found in polymer layers such as Chronoflex or Bionate55. The external wall of the implant may be coated and/or impregnatedwith a latticework of polymer surface sprayed or layered on the outsideof the implant to promote cartilage tissue regeneration. This mostexternal surface coating may contain living chondrocytes as in theCarticel procedure by the Genzyme company, and/or may contain stem cellswith directed gene mutations to enhance adherence of the coating to theimplant. The living cells may be imposed in between troughs while thesurface areas of prominence may be used for space validation, traction,and cell protection.

The implant embodying features of the invention may be used in a seriesof treatments wherein the first treatment involves use of autologous orminimally manipulated allograph interpositional tissues or xenograph,the second treatment involves the use of the same type of tissue addedto stem cells or chondrocytes and the third treatment involvingdeployment of the implant if the first two fail or are ineffective.

The implant may be provided with latticework or other reinforcingstrands, preferably on the exterior or within the wall thereof tocontrol the maximum expansion of the implant when deployed at theorthopedic site.

The method of insertion of the ankle implant generally will be throughan anterior surgical ankle approach or tendon separating incision fromthe distal tibia to the proximal talus (or calcaneus if the talus isabsent), removing and reconstructing portions of the superior andinferior ankle extensor retinacula only to the extent required to gainaccess to the cleared tibiotalar space. Analogous to the hip jointinsertional method, the ankle joint will be prepared arthroscopicallyunder general anesthesia, and may benefit from distal distraction as intotal ankle joint replacement surgeries with the DePuy Agility techniquepinning above and below the ankle joint and then distracting it. Thedegree of distraction required in all joints to which this invention isapplied, including but not limited to those of all appendicular skeletalstructures such as the shoulder, elbow, wrist, phalanges, hip, knee, andankle, will depend both on the nature anatomy and locatedpathophysiology that must be accommodated on a case by case basis andsaid distraction may be a combination of body position usinggravitational forces and/or superimposed distracting devices. In theankle, the surgeon will be developing the interval between the extensorhallucis longus and anterior tibial tendons. Injury tissue is removed,and the implant inserted fitting as preplanned. The implant surface maybe provided with roughness, e.g. external mesh, to control movement byfriction as described above for the hip joint, and/or attached fixationcords or tabs to connect to proximate ligaments or adjacent boneystructures may be used at the surgeon's discretion to balance implantlocation stability and integrity, with the need for functional jointmovements.

Over time, ingrowth of repair tissue aids in fixation and stabilityexternally to the implant, while the soft cushioning implant interiorwill absorb forces across the joint surfaces and permit proper motion.The tugor or wall tension of the implant as well as the insidedistension of the implant per se can be adjusted by adding or removingthe inflation substance to the implant's interior space.

Accordingly, the present invention provides a new approach toarthroplasty that involves a resilient implant device deployed betweenbones of the joint. Whereas a joint is comprised of the interfacebetween bone cartilage space cartilage bone, in certain joint spacessuch as the knee, the invention cushion may expand to fit the spacesbetween both “knee joints”—the femoral tibial involved on standing orwalking on a level plane, and the patella femoral bones of the knee moreinvolved on stair ascent and decent. For example, pressures behind theknee cap or patella when lying are zero, when standing are 0.7 timesbody weight, and when going up and down the patella femoral pressuresare 3-4 times body weight. Thus, the implants will need to accommodateall the normal body functional pressures and complex space movements, asdescribed above also in the ankle. When in the hip joint, the normalflexion up to 120 degrees, extension of 20 degrees, abduction of 50degrees, internal and external rotation of 45 degrees will producevariable axial, shear, and cyclic loads which the implant by design willaccommodate and endure as up to 6 times body weight, consistent with atire on a car that allows for cyclic loads different when drivingstraight or turning corners. The implant embodying features of thepresent invention provides more physiologic motion and shock absorptionwithin the joint and has combined characteristics of anatomic designsymmetry, balanced rigidity with sufficient attachment connections toadjacent normal structures, and durability that meet the needs of jointreconstruction.

The opposing internal surfaces of the first and second walls of theinvention may either move together in synchrony or in oppositedirections from one another (e.g. the superior wall moving medially inthe hip and the inferior wall moving laterally). Optionally, the implantmay be fixed to a concave surface of the joint (e.g., the acetabular hipcup) or to a convex surface of the joint (e.g. the dorsal femoral headsurface), to both, or to neither (e.g., having an interference fitwithin the joint with an expanding balloon or cushion that fills theexisting space). The implant may be inserted arthroscopically like adeflated balloon and then inflated through a cannula into the ankle orhip (or other joint structure) to act as a cushion or renewed interfacefor painless and stable limb motion. When feasible joint capsular andadjacent ligament tissue as well as bone will be left in place topreserve the natural body, unless interfering with reconstructed limbfunction.

The application of steam in addition to removing damaged debris, cansmooth out and reform the joint surface. The high temperature of thesteam tends to weld cracks or fissures which can be present in thecartilage surface of a damaged joint. Smoothing of joint surfacecartilage with steam welds or seals existing cracks or flaps in thecartilage, especially superficially as the lamina splendors, which melttogether to provide a white shiny gliding joint surface. In cases wherebone is exposed, the steam can be used to stabilize the periphery of thedefect in the joint surface via capsulorrhaphy or joint tightening. Openmechanical and chemical debridement may also be employed to prepare thesurfaces for the implant.

Once the implant is secured to the femoral head by means of the skirt ortabs, an impregnated transfer medium or cell template may be used, asdescribed by Histogenics and Tygenix chondrocytes delivery systemswherein the position of concentrated cells is mechanically placed aboutthe implant at areas of greatest cartilage damage to promote regrowth,or as in Carticel wherein watery cells are implanted beneath aperiosteal membrane (a wall of the implant serving as the membrane),prior to completion of the inflation or expansion of the implant. Atsyringe or gauged device with measured screw-home pressure is used toinflate the implant.

Once the joint is ready to receive the implant, the deflated implant isadvanced through the diaphragm of a delivery cannula (such as the Acufexfrom Smith & Nephew) and into the joint. It can be inflated by theattached cannula using a common syringe, inserting several cc's offiller material. Inserted contents and locations of cell placementsdepend on areas of need and joint size. In the hip implant several cc'sof filler material and a viscolubricant in the interior of the implantwill allow distension, cushioning, and gliding movements. Cellregeneration agents are placed in the areas of greatest need.

Methods of living stem cell or chondrocyte placement depend on thelesions and specific implant construct. Direct infusion into the jointwith completion of implant inflation will press the cells into thehyaline surface, whereupon they attach within the first 24 hours. As aresult, the patient should remain sedentary and the joint where theimplant is deployed, non-weight bearing for the first day after surgery.Deeper osteochondral defects can be treated by ‘hyper-perfusion ofcells’ via either 3-D cell transfer templates, or microneedle injectionas used in treatment of diabetic patients for blood sugar testing andinsulin/transdermal drug delivery. The cannula attached to the implantmay be sealed and detached, or left in place for periodic aspiration ofnoxious enzymes as for the Cox-1, Cox-2, and 5-Lox systems, followed byreinsertion of activated substances including viscolubricants, or evenmore cells.

Implants embodying features of the invention may be designed forpermanent or temporary deployment within a joint structure. Moreover,the implant may be formed of suitable bioabsorbable materials so thatthe implant may be absorbed within a particular predetermined timeframe. Suitable bioabsorbable materials include polylactic acid,polyglycolic acid, polycaprolactone, copolymers, blends and variantsthereof. One present method of forming the implant is to apply numerouslayers of polymer such as ChronoFlex AR in a solvent and evaporating thesolvent after applying each layer.

The skirting or fixation tabs of the present implant prevent jointmigration during use. This is in contradistinction with prior solidpolymer implants that tended toward dislocation and poor post operativefunction.

While particular forms of the invention have been illustrated anddescribed herein, it will be apparent that various modifications andimprovements can be made to the invention. One alternative implantconstruction involves the use of an upper portion of the implant havinga net-like construction and filled with balls or ball bearing likeelements that are larger than the openings in the netting. The balls orball bearing like elements provide motion to the implant. The nettingand ball bearing like elements may include regeneration agents aspreviously discussed, and the bearing construction may be directedtoward favorable implant movement balanced with content disbursement.

The invention is intended primarily for human use but may be extended tomammalian use. To the extent not otherwise disclosed herein, materialsand structure may be of conventional design.

Moreover, individual features of embodiments of the invention may beshown in some drawings and not in others, but those skilled in the artwill recognize that individual features of one embodiment of theinvention can be utilized in another embodiment. Moreover, individualfeatures of one embodiment may be combined with any or all the featuresof another embodiment. Accordingly, it is not intended that theinvention be limited to the specific embodiments illustrated. It istherefore intended that this invention be defined by the scope of theappended claims as broadly as the prior art will permit.

Terms such as “element”, “member”, “component”, “device”, “means”,“portion”, “section”, “steps” and words of similar import when usedherein shall not be construed as invoking the provisions of 35 U.S.C§112(6) unless the following claims expressly use the terms “means for”or “step for” followed by a particular function without reference to aspecific structure or a specific action. All patents and all patentapplications referred to above are hereby incorporated by reference intheir entirety.

What is claimed is:
 1. A resilient orthopedic implant comprising: a. afirst wall configured to engage an articulating end of an acetabulum ofa pelvic bone; b. a second wall configured to conform around a portionof a femoral head, the second wall having one or more appendagesconfigured to secure the second wall to the femoral head; c. a side wallextending between the first wall and the second wall and configured tofacilitate relative motion between the first and second walls; and d. aninterior portion configured to be directly enclosed by the first wallthe side wall, and a proximal end of the femoral head; wherein somelength of the first wall overlaps some length of the second wallcreating a fold in the implant such that some length of an exteriorsurface of the side wall has a concave shape at the fold; and whereinthe implant is configured for deployment between the femoral head andthe acetabulum of the pelvic bone when neither the femoral head nor thepelvic bone is resected.
 2. The implant of claim 1 wherein the one ormore appendages is a skirt.
 3. The implant of claim 1 wherein the one ormore appendages are tabs.
 4. The implant of claim 1 wherein the one ormore appendages are chords.
 5. The implant of claim 1 wherein therelative motion between the first and second walls is rotational motion.6. The implant of claim 1 wherein the relative motion between the firstand second walls is linear or curvilinear motion.
 7. The implant ofclaim 1 wherein the relative motion is rotational motion and linear orcurvilinear motion.
 8. The implant of claim 1 wherein the one or moreappendages are configured to be secured to the femur by an adhesive. 9.The implant of claim 1 wherein the first wall has an exterior surfacewith a convex shape which is configured to contact the acetabulum. 10.The implant of claim 1 wherein the implant comprises a resilientmaterial.
 11. The implant of claim 10 wherein the resilient material isa biodurable thermoplastic polyurethane.
 12. The implant of claim 10wherein the resilient material is bioabsorbable.
 13. The implant ofclaim 1 wherein one or more of the walls comprise a plurality of layers.14. The implant of claim 13 wherein at least one of the layers isporous.
 15. The implant of claim 1 wherein the side wall of the implanthas reinforcing strands to control expansion upon compression of theimplant.
 16. The implant of claim 1 wherein the interior portion isconfigured to be filled with an inflation medium.
 17. The implant ofclaim 16 wherein the inflation medium is a resilient material.
 18. Theimplant of claim 1 wherein a lubricious material is maintained betweenthe first and second walls to facilitate relative motion between thefirst and second walls.
 19. The implant of claim 1, wherein the firstwall or the second wall is composed of biocompatible polymericmaterials.
 20. The implant of claim 1, wherein the first wall, secondwall, or side wall comprises numerous layers of one or more polymers.21. The implant of claim 1, wherein the first wall, second wall, or sidewall comprises biocompatible polymeric materials.
 22. The implant ofclaim 1, wherein at least one of the first wall, second wall, or sidewall incorporates a lattice.
 23. The implant of claim 22, wherein thelattice is configured to hold a therapeutic agent in proximity of anosteochondral defect.
 24. The implant of claim 22, wherein the latticecomprises a biocompatible polymer.
 25. The implant of claim 1, furthercomprising a conduit the conduit configured to provide access to theinterior portion for injection of a biomaterial into the interiorportion while the second wall is fixed to the portion of the femoralhead.